Light responsive continuously tested tripping device for electric circuit breaker



May 12, 1970 ELECTRIC CIRCUIT BREAKER Filed MW. 2, 1966 TESTED TRIPPINGDEVICE FOR 2 Sheets-Sheet 1 Fa i i P 3 I 2o L i N J; a. I

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Y. PELENC 3,511,999

TRIPPING DEVIC May 12, 1970 E FOR LIGHT RESPONSIVE CONTINUOUSLY TESTEDELECTRIC CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed NOV. 2, 1966 UnitedStates Patent Office Int. Cl. I-l01j31/50 U.S. Cl. 250-214 6 ClaimsABSTRACT OF THE DISCLOSURE A monitoring circuit for checkingphoto-electric trip ping devices in high voltage lines including aphotoelectrically controlled switch and a disabling device operable toprevent switching in the absence of current in the high voltage line.

This invention relates to photo-electric control devices for tripping ahigh-voltage circuit-breaker.

The constant endeavour to reduce the tripping time of high-voltagecircuit-breakers has led designers to consider replacing theconventional hydraulic, pneumatic or hydro-pneumatic devices by aphoto-electric device. In such a photo-electric device the spaceseparating the parts of the breaker which are at the high-voltagepotential of the line or power circuit in which the circuit breaker isinserted from the parts which are at or near earth potential is bridgedby a light beam. The beam is emitted by a light source which is usuallyformed by flash tube at earth potential which discharges in a gaseousmedium. The flash at earth potential is turned on or ignited when thebreaker is to be tripped or opened for instance in case of a major faultin the power circuit, and the light beam emitted by the flash isconducted by a light guide to the high-voltage region of the circuitbreaker to trigger a photo-electric cell, which controls in turn anelectromagnetic tripping device such as a relay, for example by means ofa controlled rectifier, such as an SCR.

Generally, these photo-electric control devices are combined with aconventional control used for the normal opening and closing of thecircuit breaker, and are intended to function only in the case of amajor fault on the power system because of their short response time. Inthe case of a high-voltage circuit-breaker having a plurality ofbreaking or switching elements which are electrically connected inseries for each pole, each breaking element generally has its owntripping device, and it is obvious that it is necessary to avoid thetripping of only a single breaking element in the case of a major faulton the power circuit, such as a short circuit. This condition has givenrise to the design of testing devices capable of detecting the properoperating state of the tripping circuit of all breaking elements. Inthis way, a tripping order can be avoided if one of the trippingcircuits of one .of the breaking elements is not in its normal properoperating condition in which it is capable of responding correctly tothe given order. Known testing 3,511,999 Patented May 12, 1970 devicesof this kind test the various tripping circuits only immediately priorto the transmission of a tripping order. It is obvious that such a testneeds time, however short this time may be, and that this does not allowthe' immediate execution of such a tripping order.

It is an object of the present invention to solve this problem byeliminating this preliminary test, through carrying out a continuoustesting of the tripping circuits.

The invention will be further described, by way of example, withreference to the accompanying drawings, showing embodiments thereof, andin which:

FIG. 1 shows the diagram of a photo-electric tripping device for onepole of a high-voltage circuit-breaker comprising a single breakingpoint; and

FIG. 2 shows a part of a photo-electric tripping device for a circuitbreaker having per pole two breaking elements which are electricallyconnected in series.

In FIG. 1, the parts of the tripping device shown inside the rectangle Tare located in a control panel disposed on the ground and at or nearearth potential. The parts at the potential of the high-voltage line Lof the power system in which the circuit breaker is installed are showninside the rectangle P.

At ground level, a source of electrical energy 10 may be connected tothe terminals of the filament of a flash tube 11 (forming the flash orlight source) through the contacts of a fault relay 12 and through agate circuit 13. The gate circuit 13 is shown diagrammatically and maycomprise essentially an SCR, or any other suitable known switchingdevice which does not form part of the invention.

The gate circuit 13 is controlled by a photo-electric cell 14 capable ofgating on the gate when it is illuminated under the conditions mentionedfurther below, and of gating off, that is to say, of interrupting thecircuit connecting the source 10 to the light source 11, in the casethat the device 14 is not illuminated. The flash 11 may direct a lightbeam through a light guide 15 onto a photo-electric cell 16 located tothe live part P of the circuit-breaker.

The opening of the moving contact of the breaking element, showndiagrammatically at 17, is controlled by a suitable electromagnetictripping device or control relay having a coil 18. A source of electricenergy is formed by a capacitor 19, supplied directly by thehigh-voltage line L through a current transformer 20 and a rectifierbridge 21. SCRs 22, 23 in anti-parallel connection serve to limit thevoltage at the terminals of the bridge 21, when the line current is toohigh, and resistors 24, 25, connected to the control electrodes of thediodes 22, 23, energize the same. The capacitor 19 is connected to thecoil 18 through an SCR 26 or another controlled valve means or solidstate switch whose control electrode may be excited if the cell 16 isilluminated and triggered; this cell is connected on the other side toone terminal of the capacitor 19 through a resistor 27. A lamp or otherlight source 28 is connected in series with a current limiting resistor29, and the whole assembly is connected in parallel to the mainterminals of the SCR 26. A capacitor 30 of lower capacity than thecapacitor 19 is connected between the cathode of the SCR 26 on the onehand, and

the junction of the resistor 29 and the lamp 28 on the other hand. Thelatter can illuminate the cell 14 through a second light guide 31bridging the space between the parts under high voltage and those atearth potential, and which may possibly be the same as, or be combinedwith, the first guide 15 to form a single unit. Lenses 32, 33 and 34enable the beams passing through the guides 15 and 31 to be focussed.

All the breaking elements of the circuit-breaker are equipped with adevice according to the drawing, but certain parts shown in therectangle T may be common to different breaking elements of one or morepoles, as explained with reference to FIG. 2. In this figure, therectangles P and P show the high potential regions of two breakingpoints of the same pole of a circuit breaker. For the sake ofsimplification, there are shown only the two lamps 28, 28' and the twophoto-electric devices 16 and 16 but each rectangle P and P of FIG. 2actually contains all the elements of the rectangle P of FIG. 1. Thesingle flash 11 illuminates through two guides 15, 15 two cells 16, 16'of two breaking points 17, 17' mounted in series on the line L. The gatecircuit 13 is common to the two breaking points and is controlled by thetwo cells 14, 14'. In all cases, the absence of energizing byillumination of a single cell 14 has the result that no flash 11 canfunction.

The arrangement of FIG. 1 as shown functions as follows:

With the main contacts 17 of the breaker point of a breaker pole beingclosed, the conductor L carries a current which charges the capacitor 19across the transformer 20 and the bridge 21. If the circuit of the coil18 is not broken and if the SCR 26 is not short-circuited, a normalOFF-state voltage appears at the main terminals of the latter and thedetecting lamp 28 lights up. The cell 14 is therefore illuminated andunblocks the flash 11 by enabling the gate circuit 13. I

The proper functioning of the SCR 26 is thus checked, but for reasons ofsafety it is advisable to double or triple this element to provide twoor three parallel SCRs.

It should be noted that the monitoring or testing system is capable ofdetecting the most frequent fault of an SCR, namely itsshort-circuiting. In fact, in this case, no voltage can appear at theterminals of the light source 28, so that the cell 14 is not triggeredand cannot enable the gate circuit 13 which now blocks the flash 11.

The optical transmission is effected by means of tubes made of glass orPlexiglas which may be Water-tight, filled with an inert gas and havingan inner diameter of the order to 10 to 20 millimeters.

If the tripping circuit is in its proper operating condition and atripping order is given by the relay 12, in case of fault of thehigh-voltage circuit, the light source 28 illuminates the cell 14 sothat the flash 11 may be energized and send a light beam onto the cell16 of the pole, causing the turning ON of the SCR 26 and the dischargeof the capacitor 19 across the coil 18. The breaker contacts 17 open andthe fault on the high voltage circuit is eliminated.

As may be seen from FIG. 2, if a single one or both of the cells 14 or14' are not illuminated owing to a fault in the corresponding highvoltage parts of the tripping circuit of the breaking points 17 and 17',an order for tripping or opening of the breaking points 17 and 17 givenby the relay 12 cannot pass through the gate circuit 13 so that nobreaker element can receive the tripping order.

The lamp 28 which remains generally illuminated has a low light output.It has been found that this type of lamp needs a certain time forreaching its full light output after a voltage has been applied thereto.In order to prevent the illumination of the cell 14 from being too weakunder these circumstances immediately after the closure of thecircuit-breaker to unblock the Cir flash 11 without delay, and thus toavoid that a tripping order is not carried out in the case of closure ofthe circuit-breaker in case of a fault on the high-voltage system, inspite of the good state of the tripping circuits, the capacitor 30* hasbeen provided which enables the application of an overvoltage to thelamp 28 for a few moments after it has been energized. The cell 14 nowis sufficiently illuminated at the closure of the circuitbreaker toenable the ultra-rapid tripping immediately after the closure of thecircuit-breaker.

Obviously, the described embodiments may be modified in many wayswithout departing from the principle of the invention. For example, thecell 16 may be combined with the SCR 26 by using a photothyristor.

What I claim is:

1. A light responsive continuously tested tripping device for a breakingelement of a circuit breaker, comprising:

(a) a first light source,

(b) energizing means for electrically energizing said first light sourcein response to a tripping order,

(c) first photo-electric means responsive to the light emitted by saidfirst light source,

(d) control means for operating said breaking element,

(e) electronic switching means controlled by said first photo-electricmeans, said electronic switching means being operatively connectetd tosaid control means to operate said control means in response to thetriggering of said first photo-electric means by the light emitted bysaid first light source,

(f) sensing means for continuously detecting the presence of a normalOFF-state voltage across said electronic switching means, and

(g) inhibiting means for rendering inoperative said energizing means inresponse to the disappearance of said normal OFF-state voltage.

2. The device of claim 1, in which said sensing means further comprisesa second light source energized by said normal voltage, said inhibitingmeans being controlled by second photo-electric means responsive to thelight emitted by said second light source.

3. The device of claim 2, in which said inhibiting means comprise anelectronic gate circuit gating said first light source and electricallycontrolled by the output voltage of said second photo-electric means.

4. The device of claim 2 for tripping of a breaking element of a circuitbreaker inserted in a high-voltage power line, wherein said firstphoto-electric means and said second light source are located in thehigh voltage region of the circuit breaker, said first light source andsaid second photo-electric means being located in a lowvoltage region ator near earth potential.

5. The device of claim 2 further comprising means for applying atransient overvoltage to said second light source at the moment ofappearance of said normal voltage.

6. A light responsive continuously tested tripping device for at least apair of series connected breaking elements of a circuit breaker,comprising:

(a) first light emitting means responsive to a tripping order,

(b) first and second photo-electric means responsive to the lightemitted by said first light emitting means,

(c) first and second control means for respectively operating saidbreaking elements,

(d) first and second electronic switching means respectively controlledby said first and second photoelectric means and operatively connectedrespectively to said first and second control means to operate saidcontrol means in response to the triggering of said first and secondphoto-electric means by the light emitted by said first light emittingmeans,

(e) second and third light emitting means respectively 5 6 energized bythe normal OFF-state voltages of said first and second electronicswitching means, erences Clted (f1 tillilrdragttifourthtiphoto-eletctit;J meags respoinsivg UNITED STATES PATENTS o e 1res ec ve emi e sai secon an third ligfit emitfing and Y 3,2 9,154 9/196M rm 4 (g) inhibiting means controlled by sald third and fourthphoto-electric means so that said first light RALPH NILSON PnmaryExammer emitting means can only be energized when both M. ABRAMSON,Assistant Examiner said third and fourth photo-electric means aretriggered by the light emitted respectively by said sec- 10 0nd andthird light emitting means energized by 317 124 the normal OFF-statevoltage of respectively said first and second electronic switchingmeans.

